1. Field of the Invention
The present invention relates generally to the field of recovering nutrients from cheese whey and more particularly to a method of improving the handling characteristics of deproteinized cheese whey.
2. Description of the Prior Art
It is known in the art that it is beneficial to recover valuable nutrients from cheese whey. Many billions of pounds of whey are produced each year as a byproduct of the cheese industry and it has been found desirable to recover nutrients from this material to derive economic benefits therefrom and to avoid having to dispose of whey which is so high in BOD and COD loadings. The economic benefits result from the use of the nutrients in place of other dairy or meat products, and the disposal benefits have aided in the control of cheese plant pollution of our streams and rivers.
The simplest way of recovering such nutrients is to merely dry the whey and use the product as an animal feed. More sophisticated techniques, however, have been developed in attempts to recover the highly desirable protein and lactose fractions of the whey. The proteins may be used in milk replacers, as high protein feed supplements and as food enhances, while the lactose material is very suitable for use by the bakery industry and has considerable food and energy value.
The earliest attempts at separating components of whey involved chemical treatments such as pH adjustment, heating, flocuation, etc. and resulted in low quantities of highly denatured products. Electrodialysis has also been attempted to remove salts, but this process is slow and expensive.
More recently, the techniques of ultrafiltration and reverse osmosis have been adapted for treatment of cheese whey. In reverse osmosis, a semipermable membrane is flanked by a concentrated solution and a dilute solution. Natural forces would cause liquid to flow through the membrane to equalize the solute concentration, but in reverse osmosis, a pressure is applied to the concentrated side to force water through the membrane, opposite to normal osmostic flow, to further concentrate the material. In ultrafiltration, on the other hand, pressure is applied to a solution to force a permeate through a semipermeable membrane. If, for example, the openings of membrane are sized to pass all portions of the whey except the proteins, the proteins will become concentrated and a permeate (which contains water, lactose, ash, salts and other materials) will pass through the membrane.
One highly successful method for recovering nutrients from cheese whey is described in my U.S. Pat. No. 4,001,198 issued Jan. 4, 1977 for "Method of Recovering Nutrients from Cheese Whey and Purifying the Effluent." The method described therein produces dry food quality protein and lactose powders from cheese whey by sequential ultrafiltration processes, each of which removes as permeate substantial amounts of water and dissolved solids from the respective concentrates. Cheese whey from the cheese plant is first passed through a separator and then strained, cooled and delivered to a holding tank. The whey is then passed through spiral wound ultrafiltration modules to separate a protein rich concentrate and a permeate which contains the lactose and other materials. The protein concentrate is pasteurized, cooled and then evaporated and spray dried to form one final product from the method. The permeate is treated further by passing it through a second ultrafiltration unit, this one having a membrane selected for the rejection of lactose. A lactose rich concentrate is formed and a second permeate is produced. In the process of the above-mentioned patent, the concentrate is washed and further concentrated and the lactose crystals are prepared by subsequent vacuum evaporation and drying steps. The permeate from the lactose concentration is subsequently treated in my process by a third ultrafiltration step to remove fine solids and the permeate resulting from that step is treated with oxygen to lower the BOD of the final effluent.
While the process just described is highly beneficial, problems have been encountered with handling of the lactose containing permeate, especially in the evaporation of same. Similar problems also exist where other methods of removing protein (i.e. other than ultrafiltration) have been employed to produce deproteinized whey.
The basic problem is that the permeate is difficult to evaporate because of precipitation of calcium containing products (primarily phosphates) on the heat exchange surfaces of the evaporators. The precipitation results in decreased heat exchange efficiency and leads to greater evaporating costs. The precipitate is also difficult to remove, leading to increased down time and cleaning chemical costs. Moreover, it has been discovered by the present inventor that certain components in the deproteinized whey have valuable uses and that recovery of same could result in economic benefits as well as the elimination of handling problems.
One example of the foregoing is that it is desirable to manufacture a dicalcium phosphate, lactose, protein mixture as an aid in controlling melt and as an extender in the manufacture of cheese products. This is typically accomplished by dry blending the various ingredients. Recovery of the dicalcium phosphate as part of the process for preparing the lactose and protein would be beneficial and would also eliminate the fouling characteristics inherent in evaporation of the permeate. Another use for deproteinized whey is as a hydralized syrup. In this known process, deproteinized whey is cooled to 85.degree. F., innoculated with lactose enzyme and incubated for a selected period. The material is then passed through an ultrafiltration module to prepare a concentrate which has a volume of about 2% of the original volume, the concentrate being used to reinnoculate another batch. However, with this process, fouling of the ultrafiltration membrane with calcium containing materials occurs and the process could be improved by removal of same. A technique for improving the handling characteristics of deproteinized whey in these and other processes for using deproteinized whey would be a significant advance in the art.